add 'container' option motivation to tooltip docs

docs/_includes/js/tooltips.html

@@ -95,7 +95,7 @@ $('#example').tooltip(options)
          <td>string | false</td>
          <td>false</td>
          <td>
-          <p>Appends the tooltip to a specific element. Example: <code>container: 'body'</code></p>
+          <p>Appends the tooltip to a specific element. Example: <code>container: 'body'</code>. This option is particularly useful in that it allows you to position the tooltip in the flow of the document near the triggering element - which will prevent the tooltip from floating away from the triggering element during a window resize.</p>
          </td>
        </tr>
        <tr>